This disclosure relates to separation of bitumen and kerogen, which are highly viscous varieties of petroleum, from oil sands, tar sands, oil shale, and other sources of petroleum bound to a substrate, sometimes referred to as unconventional petroleum or oil. There are large reserves of such petroleum ore in North America that are underutilized due to the economic and environmental costs of extracting usable petroleum from these deposits. The current surface mining processes recover approximately 91% of the bitumen in the ore. It is desired to improve the bitumen yield and reduce production costs.
One approach to improve the bitumen recovery rate is to heat the process water, reducing the viscosity of the bitumen. The viscosity of bitumen is reduced by a factor of 10 by heating it from 40° C. to 67° C., and is further reduced by a factor of more than 2 by further heating it from 67° C. to 80° C. Froth diluted with naptha will experience similar viscosity decreases with increasing temperatures.
The throughput rate for settling tanks, settling devices, centrifuges, and cyclones is inversely proportional to viscosity. Increasing the bitumen temperature from 40° C. to 80° C. can increase settling rates by a factor of 20, or decrease the size of the smallest particles extracted by a factor of 4.5 for the same processing rates.
Nonetheless, it is not economically feasible to heat the entire process to 80° C., as this requires too much energy per barrel of extracted hydrocarbons. The bitumen is a minor constituent through much of the process, and a large amount of process water is used. Much of the process water leaves the system, either as liquid or as vapor, and much of the heat introduced is lost.
Current technology heats the entire process to a certain extent, and utilizes steam injection to increase the temperature of the slurry at certain process points where a higher temperature may improve process efficiency.